Add PhamePost to full text search

Summary: Adds PhamePost object to fulltextsearch index. Some issue searching just "Open" though? Also "closed" objects search fine but don't display as disabled.

Test Plan:
bin/search index --type POST

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T9897

Differential Revision: https://secure.phabricator.com/D16116